Molded resin articles have been decorated in the past with graphic and/or indicia patterns (such as letters, figures, symbols and the like) using known foil-decorating techniques. According to the foil-decorating technique, a molded surface-patterned article is prepared by placing in a mold cavity a resin film bearing a selected graphic and/or indicia pattern, filling the mold cavity with a molten resin (or a resin prepolymer) and then compressing the thus obtained molded article under heat and pressure to integrate the film onto a surface of the molded article. In the case of thermosetting resins, this heat and pressure treatment serves to cause the resin to react further.
The foil-decorating technique has been used extensively to decorate the surfaces of molded articles formed of thermosetting resins (e.g. melamine resin) with pictorial patterns. However, when thermosetting resins are used to form surface-patterned articles, the steps employed in foil-decorating become relatively complex thereby increasing the costs associated with manufacturing such articles. Accordingly, the use of foil-decorating techniques using thermoplastic resins has recently gained more attention because molded articles of thermoplastic resins are more easily obtained by injection molding techniques, resulting in lower production costs. In this regard, foil-decorated injection-molded articles using polyolefins, such as polypropylene have been commercialized.
The thermoplastic polyolefin resins that have typically been used in foil-decorating techniques generally exhibit poor heat resistance, strength and rigidity. Thus, although these typical resins can be used to form injection-molded articles that may be employed in some end-use applications, they cannot usually be employed in end-use applications where severe conditions may be encountered. In the case of injection-molded tableware, food vessels or trays, for example, a number of additional performance requirements must be met. Specifically, the odor and/or color of food must not migrate into the resin. Conversely the odor and/or "taste" of the resin should not migrate into the food.
Molded articles satisfying all of the foregoing requirements have not been developed to date. It is therefore towards fulfilling such a need that the present invention is directed.
The present invention broadly resides in foil-decorated surface-patterned articles formed of polybutylene terephthalate (PBT) resin. In this regard, PBT resins have not been used previously as a substrate body for foil-decorations.
More specifically, in accordance with the present invention, a process for preparing a surface-decorated polybutylene terephthalate resin molded article (i.e., having a graphic and/or indicia pattern formed on a surface of the article) is especially characterized by placing a film composed mainly of a polybutylene terephthalate resin, and back-printed with the desired pattern, in a cavity of a mold so that the printed surface of the film will be in contact with the subsequently injected resin. The PBT film further includes a coating layer of adhesive applied over the printing on the back side thereof (i.e. so as to come into contact with resin injected into the mold cavity). Molten resin comprised of polybutylene terephthalate is then injected into the mold cavity to fill the same and to integrally bond the pattern-printed film onto the surface of the resulting molded resin article. The resulting equally novel molded article prepared according to this process will thereby have a surface which corresponds to the film, and will exhibit the pattern associated with that film.